Optoelectric composite wiring boards, which are printed circuit boards having build-in optical waveguides, are attracting attention as a way of solving the problems of high-frequency noise and insufficient transmission bandwidth associated with higher signal speeds within various types of information processing devices today.
Optical waveguides with an optical waveguide core having an inclined endface capable of reflecting light are formed in such optoelectric composite wiring boards for, e.g., light input and output from optical waveguides. An example of a method of manufacturing an optical waveguide core having such an inclined endface is the method described in Non-Patent Document 1 below.
Non-Patent Document 1 describes a method of manufacturing an optical waveguide core which includes the steps of forming an optical waveguide core, forming an inclined endface for a mirror on the optical waveguide core by machining the optical waveguide core with a rotary blade or the like, and forming a mirror by depositing a layer of metal on the inclined endface so as to increase the reflection efficiency at the inclined endface.
Non-Patent Document 2 below describes a method wherein an optical waveguide core is formed, following which ablation is carried out by irradiation with an excimer laser from a 45° direction, thereby forming a 45° inclined endface for a mirror.
Patent Document 1 below describes a manufacturing method that includes a manufacturing step wherein light is selectively irradiated onto a photosensitive material layer so as to alter the photosensitive material and thereby form a structure, which manufacturing method includes a step wherein the light is made to enter a substrate at a specific angle. More specifically, it discloses that a waveguide having a 45° mirror can be formed by carrying out, in order: core coating, 45° exposure, and development.
Non-Patent Documents 1 and 2 disclose that an optical waveguide core having an inclined endface can be formed by the above-described manufacturing methods.
At the same time, in the manufacture of optical waveguide cores having an inclined endface, it is desired to increase the manufacturing efficiency by reducing the number of steps required to manufacture an optical waveguide core having an inclined endface in addition to the ability to form an inclined endface. Moreover, there also exists a desire to hold down the manufacturing costs by reducing the number of manufacturing steps.
In the methods described in Non-Patent Documents 1 and 2, following formation of the optical waveguide core, an inclined endface is formed by a cutting operation or the like. That is, formation of the optical waveguide core and formation of the inclined endface are carried out separately, which tends to result in a lower production efficiency and higher production costs than when both are carried out at the same time.
In this connection, Patent Document 1 discloses art which enables the formation of an optical waveguide core and the formation of an inclined endface to be carried out at the same time by having the light at the time of exposure enter a substrate at a specific angle.